1. Field of the Invention
The present invention relates to a cooler having a multi-compartment gradient cooling construction and a plurality of folding wheels for easy portability; and more particularly, to a cooler having an ice-cold storage compartment, a dry moderately-cold storage compartment, and a dry non-cold storage compartment, as well as means providing for selective entry into each of the compartments and for sealing each of the compartments from the others to afford optimal cooling benefits and prevent water entry into the dry compartments.
2. Description of the Prior Art
Portable coolers used for storing food, beverages, and other perishable items are commonly utilized by consumers. The coolers heretofore devised and utilized are known to generally consist of single food storage compartments and multi-compartment cooler systems typically focusing on the separation of beverages from food items. These coolers do not provide the most optimal refrigeration, as they do not distinguish between the different temperatures and moisture sensitivities required for storing food items and non-food items. None of the heretofore disclosed coolers sets forth a cooler comprised of a multi-compartment gradient cooling construction, with wet and dry sealed compartments, with selective entry, and a plurality of folding wheels for easy portability. 
Certain food items require very low, or ice-cold, temperatures to maintain their physical and nutritional properties, while also retaining or optimizing the taste of the product. Full immersion of the item in a cold medium, such as an ice and water mixture, provides efficient heat transfer from the item to the medium and thereby yields the most optimal conditions for maintaining the desirable ice-cold temperature. However, items that are not packaged in a water tight sealed condition are susceptible to absorbing and retaining moisture from the cold medium used. This result can be very debilitating to the integrity of the food item or non-food item, rendering the item inedible or useless. Furthermore, organization warrants a separate dry compartment for non-perishable food items and non-food items.
These moisture sensitive food items generally require cool temperatures in order to support their edible integrity, and are less appealing when served at ice-cold temperatures. Still additional moisture sensitive food products, and non-foot items, do not require cool temperatures, and are best kept at ambient temperatures. Advantageously, a separate compartment for these items enables the item to maintain the optimal temperature for the item, while retaining the integrity of the item by preventing undesirable moisture absorption.
One major disadvantage of several of the heretofore devised and utilized coolers is the failure to protect vulnerable non-sealed items from being exposed to, and subsequently absorbing cold medium's byproducts when in contact therewith; such byproducts may include water from melted ice, or other contaminants contained therein (salt, brine, etc.). As a result, these vulnerable items become saturated with water or other contaminants, yielding the item inedible and unappetizing; such as a waterlogged sandwich.
Another glaring disadvantage of several of the coolers heretofore devised and utilized is the availability of only one temperature for storage of items. With this cooler arrangement, the user cannot distinguish items that require ice-cold conditions from those items that do  not require, and are less appetizing when stored in, ice-cold conditions. Furthermore, even where there is more than one temperature disclosed, the compartments are not completely dry and are not provided with selective entry to ensure optimal insulation thereof. Still further, the disclosures do not suggest a compartment at ambient temperature contained within the cooler.
The most basic type of cooler has a single refrigerated compartment comprising an outer casing, a layer of insulation, and an innermost thermally conductive lining. For example, see the disclosures specified in U.S. Pat. No. 307,299 and U.S. Patent Application No. 2002/0060438. Specifically, U.S. Pat. No. 307,299 to Hare discloses such a cooler, but includes a layer of waterproof material between the outer casing and the insulation layer. The waterproof layer prevents the insulation layer from absorbing outside moisture, thereby preventing decay and maintaining the insulation capacity of the material. Likewise, US Patent Application No. 2002/0060438 to Gartner et al. discloses a single refrigerated compartment cooler; but in combination with a stroller for transporting children.
Similarly, other disclosures have set forth a cooler having a single food storage compartment and a vessel for storing a beverage, as set forth in U.S. Pat. Nos. 450,527; 601,798; and 6,474,097. Particularly, U.S. Pat. No. 450,527 to Poyner and U.S. Pat. No. 601,798 to Slomka (herein the '527 patent and the '798 patent, respectively) disclose dual compartment lunch-boxes, comprising a large food compartment and a smaller refreshment vessel enclosed in a container. The '527 patent merely discloses a luncheon box that does not have cooling or insulating properties. The '798 patent discloses a refrigerated lunch-box whereby the food compartment comprises a bottom area for ice and a suspended perforated tray for holding the food items. U.S. Pat. No. 6,474,097 to Treppedi et al. discloses an insulated cooler comprising a single ice food storage compartment, a separate beverage  vessel, and a pocket for the storage of spoons and forks recessed in the lid of the container and exposed to the cold therein. These single food storage compartment lunch-boxes with a separate beverage vessel are essentially tantamount to the single food compartment coolers; they share the same disadvantages.
The multi-compartment coolers heretofore devised and utilized generally consist of a plurality of compartments for the storage of food items. Separate compartments are provided for the storage of beverage items. A single lid prevents selective entry, and the compartments are typically cooled exclusively through convection or conduction means alone. These multi-compartment coolers do not provide a cooler with a cooling gradient, or range of temperatures, but only allow a single temperature. U.S. Pat. Nos. 1,895,864; 1,935,307; 4,671,079; 5,509,279; 5,605,056; and 4,286,440. For example, U.S. Pat. No. 1,895,864 to Ricci and U.S. Pat. No. 1,935,307 to Ackerman (hereinafter the '864 patent and the '307 patent) disclose insulated iceboxes to be used in vehicles, including automobile trunks, motorbuses, and airships. The compartment in the '864 patent is cooled through use of convection as the ice is stored in closed metal boxes located on either side of the storage compartment. The compartment in the '307 patent is cooled through use of a centralized compartment housing a motorized refrigeration unit that runs off of engine power.
U.S. Pat. No. 4,671,079 to Petrantoni discloses a container used to cool or heat articles. The container houses an insulated ice chamber that cools the entire container through conduction. U.S. Pat. No. 5,509,279 discloses a portable cooler to be worn on the back. The food compartment is cooled by conduction through a polymeric wall, resulting in only one temperature throughout the food and beverage compartments. U.S. Pat. No. 5,605,056 to Brown et al. discloses a portable cooler with a suspended grate for ice-free storage areas and with multitudes of drawers, but does not provide for isolated  compartments at different temperatures. None of these disclosures suggests a cooler having a cooling gradient construction wherein there are isolated, distinct compartments having varying temperatures.
Moreover, even where different compartment temperatures have been disclosed the compartments do not include a broad temperature gradient, and do not disclose differing temperatures for food item compartments; but merely provide a colder temperature for the beverage compartment. U.S. Pat. No. 4,286,440 to Taylor discloses a cooler having a central compartment comprised of a closed coolant container and a compartment for storing food items surrounded by outer compartments for beverages. Continuous circulation of the cold air currents surrounds each of the outer beverage compartments by way of convection. The cooler further comprises two lids. One lid covers the central core and another lid covers the multiple outer compartments containing the beverages. The food compartment (located in the core of the cooler) and the beverage compartment (located on the outer perimeter) are at differing temperatures, whereby the food compartment is warmer than the outer beverage compartments. The cooler disclosed by the '440 patent merely has a single food compartment set at the core temperature, and several beverage storage units surrounding the single food compartment. Beverages are generally best when consumed at ice-cold temperatures. Full emersion directly into the cooling medium is the most efficient way to cool items. A cooling medium based purely on convection is not as efficient in achieving ice-cold temperatures.
Still other multi-compartment coolers heretofore devised and utilized consist of a plurality of compartments for the storage of food items. Separate compartments are provided for the storage of beverage items. A single lid prevents selective entry, and the compartments are typically cooled through direct immersion and convection means alone. Representative  of such coolers are those described by U.S. Pat. Nos. 3,591,194; 5,295,369; and 6,193,097.
Specifically, U.S. Pat. No. 3,591,194 to Vega discloses an insulated ice chest cart having a plurality of vertical partitions. The cart is mounted on a pair of wheels and has three compartments. The compartments are not completely insulated from each other, as a lid is shared by at least two of the compartments. Ice can be used in all of the compartments, or in some of the compartments, thereby cooling the other compartments by way of convection. The walls between the compartments have holes for removal of melting ice; hence water from melted ice can seep into the neighboring chambers.
U.S. Pat. No. 5,295,369 to Garcia discloses a single lid water and ice cooler combination comprised of three compartments. Two end compartments house crushed ice, creating a wet section for storage of beverages and a central dry compartment cooled by conduction, for food items. Opening the single lid accesses all compartments of the cooler, thereby decreasing temperatures of stored, cool items. Furthermore, the water and ice cooler combination is not mounted on wheels and is not easy to transport, since tilting or shaking it causes water from the wet region to enter the dry section. U.S. Pat. No. 6,193,097 to Martin discloses a cooler comprised of a plurality of compartments for storing food and beverages. A central compartment contains ice; and the cooler has a single top cover. The central compartment has a drilled hole at the bottom to drain melted ice into the smaller bottom portion wherein the water collects. The outer compartments on either side of the central compartment are dry, but are both maintained at the same temperature through conduction.
For the foregoing reasons, there exists a need in the art for a cooler that comprises a plurality of compartments, at least two of which being dry and one of which is wet. Also needed is a cooler comprising an ice-cold storage compartment that permits full emersion of  an item. Further needed is a cooler comprising a dry moderately-cold compartment, and a dry non-cold storage compartment, and which has on its base a plurality of folding wheels for transporting the cooler. It would be highly advantageous if the use of multiple compartments at varying temperatures created a temperature gradient for maintaining temperatures ranging from ice-cold to ambient. It would also be advantageous if the multiple compartments were completely sealed from each other to allow selective entry and thus avoid disturbing the internal temperature of each compartment, while preventing moisture contamination of the dry compartments.